Bull Ants Feed at Twilight

Bull ants do not feed during all daylight hours. Observation has shown that they feed at twilight. When the sun is brighter for longer for example in summer, or there is no cloud cover, bull ants forage for food later in the day. When the sun is darker, earlier, they search for food sooner in the day. It was believed that all insects fed according to circadian rhythms, but this does not seem to be the case.

Activity in the nest was affected by cloud cover. Outside activity that involves feeding occurs at twilight. Obviously, they are feeding during these short intervals to avoid predators: most animals that eat ants would be inactive at twilight.

Tests were done at ANU in Canberra. Bull ants were put in containers where diffused light was altered. It was found they only fed when the light was set at a particular low level. Evolution does take some winding paths. This shows though that evolution develops in a rational way.